Treating Livestock with Insecticide to Control Malaria

Researchers have developed a new strategy for combating malaria in South Asia, according to a report in the current issue of the Lancet. The standard approach to malaria control in this region focuses on the indoor spraying of houses with insecticide. This method, however, is proving prohibitively expensive, as it requires large quantities of these expensive chemicals. The new study suggests that people should instead give their livestock what basically amounts to insecticide sponge baths.

Unlike malaria-transmitting mosquitoes in equatorial Africa, those in South Asia are zoophilic-that is, they feed mainly on domestic animals and only secondarily on humans. Mark Rowland of the London School of Hygiene and Tropical Medicine and his colleagues thus reasoned that applying the pesticide directly to the insects' favorite hosts might be more efficient and cost-effective than indoor spraying. To test the strategy, the team organized a trial involving six Afghan refugee settlements in Pakistan. Local veterinarians explained to the refugees that the insecticide was safe and effective, and needed to be reapplied to their cattle and goats every four to six weeks. Treatment teams recruited from the population then undertook the sponging regimen.

By all accounts, the method proved successful. In one village where malaria is particularly rampant, the treatment reduced the incidence of infection by more than 90 percent. Furthermore, the cost of the sponging regime was 80 percent lower than that of indoor spraying. Perhaps most important, the community remained enthusiastic about this malaria control campaign. This, the authors note, "probably had less to do with the health benefit to the community than with the veterinary and economic benefits to individual households." Treating the livestock with the insecticide, it turns out, eliminated many of the other parasites that plague the animals. As a result, their health and productivity increased visibly.

"The technology is simple and can be safely implemented by the community," the authors conclude. "We recommend livestock sponging as a substitute for indoor spraying wherever malaria transmission due to zoophilic mosquitoes is a risk to public health."